Combined use of biochar and sprinkler irrigation may enhance rice productivity in water-stressed regions

A 2-year field experiment was conducted to analyse the effects of fresh and aged biochar on soil properties, as well as herbicide effectiveness and rice-yield components in a Mediterranean environment. Six managements were used: no-tillage and sprinkler irrigation either without (NoT) or with first-year biochar application (NoTB), conventional tillage and sprinkler irrigation either without (ConvT) or with first-year biochar application (ConvTB), conventional tillage and flooding irrigation either without (ConvTF) or with first-year biochar application (ConvTFB). The measurements done in the first (2018) and second (2019) years after biochar addition were taken to determine its fresh and aged effects, respectively. The application of biochar led to an improvement of the soil properties such as increase in the soil's organic carbon content, pH, and dehydrogenase activity. It also reduced weed pressure, regardless of the management used, and sprinkler systems were found to have the greatest herbicide effectiveness, especially in ConvT and ConvTB. In terms of production, there were significant increases in yield with the application of fresh biochar, in the amended managements under tillage compared with their unamended counterparts. The greatest yields were found under ConvT and ConvTB, with mean values for both treatments of 10,770 and 11,299 kg ha⁻¹ in the fresh and aged years, respectively. Furthermore, water productivity reached its greatest values when sprinkler was used, especially with tillage for which the application of fresh biochar increased water productivity by a factor of 1.09 relative to ConvT. Therefore, sprinkler irrigation in combination with tillage and biochar applications can be regarded as an efficient alternative to flooding irrigation in order to ensure productive viability of rice in water-stressed regions.